Various types of fiber optic connections between adapters and plugs are known, including screw lock types, bayonet locks and the push-on lock type also known as push-pull coupling type. Umeki, et al, Japanese Showa 60-218932 discloses a push-pull coupling type. It includes an adapter equipped with an alignment sleeve and resilient catch pieces. The pieces are in cantilever form with protrusions and a claw attached to the tip of the form. The connector also includes a frame that contains an integrated ferrule and a through passageway from the rear to the front of the ferrule. The frame has protruding parts that are caught by claws of the resilient catch pieces of the adapter. A resilient inner tube shaped in the form of a round tube has an inside diameter almost equal to the outside diameter of the optical fiber cable and an outside diameter almost equal to the hole in the rear portion of the plug frame. A cord tube has a flexible part at its front end which, when inserted into the hole in the rear of the plug frame, is secured to the frame by the bending of the flexible part. The plug frame also has a finger grip mounted on its outside with raised parts. When the ferrule of the plug frame is inserted into or pulled from the alignment sleeve, the raised parts of the plug frame contact the protrusions of the cantilever form and push the resilient claws to the outside allowing the protrusions to pass. The plug frame may have a finger grip housing which is able to slide forward and backward with respect to the plug frame and, additionally, which has raised parts which release the catch of claws on the protruding parts of the plug frame when the finger grip housing is moved backward.
It is desireable that the transfer of light between the fibers of the push-pull coupling plug connector and the fiber of the adapter be accomplished with little loss of signal; i.e. with low insertion loss. Insertion loss may result from several factors, including the presence of a gap or separation between the ends of the connected fibers. Specifically, some light is lost if the end faces of two fibers are separated because light diverges as it radiates from the end of a fiber. In addition, fiber to fiber separation results in an insertion loss due to Fresnel reflections at the two glass-air interfaces between the spaced fibers. Accordingly, it is particularly important that end faces of the connected fibers of the plug and of the adapter be maintained in virtual contact with one another to minimize these losses. Contact between the fibers is improved by polishing of the fiber end faces. Typically, the end face of a fiber is polished by mounting the connector with protruding fiber to a polishing tool. The tool is then moved over a polishing medium, by hand, until the end face of the protruding fiber is satisfactorily polished.
The fibers of the push-pull coupling plug type of connectors are difficult to polish because of insecure connections between known polishing tools and the push-pull connector. With known polishing tools the polishing process is inconsistent and the results are unpredictable. For example, the fibers are often polished to such an extent that the ends of the fibers become slightly recessed within the ceramic sleeve in which they are supported. The recesses result in a gap between connected fibers which is unacceptable in connector systems. Further, with known polishing tools, it is required that skilled personnel exercise substantial care to produce acceptably polished fibers with connectors of the push-pull type.